Abstract: We investigated the behavioural and cognitive development of a captive male infant chimpanzee, Ayumu, raised by his mother, Ai. Here we report Ayumu's achievements up to the age of 2 years and 3 months, in the context of complex computer-controlled tasks. From soon after birth, Ayumu had been present during an experiment performed by his mother. The task consisted of two phases, a matching-to-sample task in which she received token rewards, and the insertion of these tokens into a vending machine to obtain food rewards. Ayumu himself received no reward or encouragement from humans for any of the actions he exhibited during the experiment. At the age of 9 months and 3 weeks, Ayumu performed his first matching-to-sample trial. At around 1 year and 3 months, he began to perform them consistently. Also during this period, he frequently stole food rewards from his mother. At 2 years and 3 months, Ayumu succeeded for the first time in inserting a token into the vending machine. Once he had succeeded in using a token, he performed both phases of the task in sequence 20 times consecutively. The infant's behaviour was not shaped by food rewards but by a strong motivation to copy his mother's behaviour. Our observations of Ayumu thus mirror the learning processes shown by wild chimpanzees.

Abstract: Techniques traditionally used in developmental research with infants have been widely used with nonhuman primates in the investigation of comparative cognitive abilities. Recently, researchers have shown that human infants and monkeys select the larger of two numerosities in a spontaneous forced-choice discrimination task. Here we adopt the same method to assess in a series of experiments spontaneous choice of the larger of two numerosities in a species of amphibian, red-backed salamanders ( Plethodon cinereus). The findings indicate that salamanders “go for more,” just like human babies and monkeys. This rudimentary capacity is a type of numerical discrimination that is spontaneously present in this amphibian.

Abstract: Recent studies on perceptual organization in humans claim that the ability to represent a visual scene as a set of coherent surfaces is of central importance for visual cognition. We examined whether this surface representation hypothesis generalizes to a non-mammalian species, the barn owl ( Tyto alba). Discrimination transfer combined with random-dot stimuli provided the appropriate means for a series of two behavioural experiments with the specific aims of (1) obtaining psychophysical measurements of figure-ground segmentation in the owl, and (2) determining the nature of the information involved. In experiment 1, two owls were trained to indicate the presence or absence of a central planar surface (figure) among a larger region of random dots (ground) based on differences in texture. Without additional training, the owls could make the same discrimination when figure and ground had reversed luminance, or were camouflaged by the use of uniformly textured random-dot stereograms. In the latter case, the figure stands out in depth from the ground when positional differences of the figure in two retinal images are combined (binocular disparity). In experiment 2, two new owls were trained to distinguish three-dimensional objects from holes using random-dot kinematograms. These birds could make the same discrimination when information on surface segmentation was unexpectedly switched from relative motion to half-occlusion. In the latter case, stereograms were used that provide the impression of stratified surfaces to humans by giving unpairable image features to the eyes. The ability to use image features such as texture, binocular disparity, relative motion, and half-occlusion interchangeably to determine figure-ground relationships suggests that in owls, as in humans, the structuring of the visual scene critically depends on how indirect image information (depth order, occlusion contours) is allocated between different surfaces.

Abstract: Although the Piagetian framework has been used by numerous researchers to compare cognitive abilities of diverse species, the system is often criticized as implemented. I examine the various criticisms, suggest ways in which the system can be improved, and argue for the need for descriptive systems such as the Piagetian framework to complement programs that look for cellular and molecular bases or mathematical models to explain behavior.

Abstract: It is possible that non-specialised cues transmitted by conspecifics guide animals' food search provided they have the cognitive abilities needed to read these cues. Macaques often check the mouth of their group-mates by olfactory and/or visual inspection. We investigated whether Tonkean macaques ( Macaca tonkeana) can find the location of distant food on the basis of cues conveyed by group-mates. The subjects of the study were two 6-year-old males, who belonged to a social group of Tonkean macaques raised in semi-free-ranging conditions. In a first experiment, we tested whether the subject can choose between two sites after having sniffed a partner who has just eaten food corresponding to one of the sites. We found that both subjects were able to choose the matching site significantly above the chance level. This demonstrated that Tonkean macaques are capable of delayed olfactory matching. They could associate a food location with an odour conveyed by a partner. In a second experiment, the same subjects were allowed to see their partner through a Plexiglas window. Both subjects were still able to choose the matching site, demonstrating they could rely on visual cues alone. Passive recruitment of partners appears possible in macaques. They can improve their foraging performances by finding the location of environmental resources from olfactory or visual cues conveyed by group-mates.